A driving device used as a conventional power conversion device adopts multiple power cells connected in series with each of phase output lines led to a three-phase load, for example, a three-phase AC motor. A three-phase AC input power is fed to a primary winding circuit of a power transformer. The primary winding circuit energizes multiple secondary winding circuits, and a three-phase power related to the secondary winding circuits is fed to the power cells respectively. The multiple power cells are connected to the respective phase output lines, and each of the power cells includes a three-phase input converter, a smoothing filter, and a single-phase output converter (refer to, for example, a patent document 1).
Patent document 1: JP-A-2001-103766